Well, I wonder if people in Japan will still want to have a proper conclusion to the series and will nag Kawamori for an OVA. ^^

That could work. An added episode 26 OVA, that's been done before by series such as Oreimo or Clannad. In fact they could do two, a Ranka and a Sheryl route like in visual novels.

Wouldn't make a difference for the continuity either, as at the end of the TV-series the main characters have completed their roles in the events of Frontier. Who ends up with who is trivial assuming future Macross shows will star a new cast anyway.